1. Field of the Invention:
The present invention relates generally to a method for cooling a wire which is being subjected to a drawing process, and more particularly to a method for cooling a wire which has undergone dry-drawing, wherein the rear portion of the die and the wire which has just been drawn to the desired dimension and which is conducted through the downstream region of the die exit are brought into direct contact with a cooling medium whereby the wire is forcedly cooled prior to the commencement or occurrence of strain-aging embrittlement within the wire.
2. Description of the Prior Art:
Heretofore, undesirable strain-aging embrittlement has occurred within, for example, steel wires which have undergone dry-drawing, and more particularly within high strength steel wires, due to the excessive temperature characteristic of the wire when drawn. It is thus desirable to reduce or eliminate such a temperature rise to a maximum extent, such as for example, by reducing the drawing speed of the wire, whereby the occurrance of surface cracking or the rupture of the wire due to the strain-aging embrittlement is prevented. In connection with such, one attempt for so eliminating aging embrittlement is known and is disclosed within British Pat. No. 1249926, such method comprising water-cooling of the wire when the same is on the rotatable drawing block. This method however has proven to be an insufficient solution to the aforenoted problems.
Another attempt is disclosed within the Japanese Utility Model Publication No. 3437/1955, wherein there is provided cooling apparatus for the wire which is to be utilized during the drawing step, wherein cooling is impressed upon the wire at a predetermined time subsequent to the drawing thereof. In addition, further attempts, as disclosed within Japanese Utility Model Publication No. 3438/1955 and Japanese Utility Model Publication No. 6429/1955, deal with air cooling apparatus for wires wherein cooling is likewise impressed upon the wires at a predetermined time subsequent to drawing. As a result, the undesirable and deleterious strain-aging embrittlement within the wire still occurs and remains unresolved.
Applicants have conducted extensive studies of dry-drawing processes of steel wires, particularly in an attempt to prevent the strain-aging embrittlement of wires, and as a result, have made the discovery that the mere water and/or air cooling of the wires, as has been suggested within the prior art, is not in fact a sufficient solution to this problem and moreover, that the temperature of the wire at the moment the wire has just been reduced to the desired dimension largely affects the aforesaid strain-aging embrittlement. Consequently, a sharp reduction or decrease in the temperature of the wire immediately subsequent to the emergence of the wire from the die is necessary in order to solve the aforenoted problems.
Continuing further, other prior art methods of drawing steel wire have also been proposed, such as for example, a wet drawing system, wherein the die is immersed within a cooling medium. These methods however are particularly applicable to the drawing of wire having a gauge less than 1 mm in diameter or when a gloss upon its surface is required. In one such method, a water-soluble or oily lubricant is used as the cooling medium, however this method suffers from the disadvantage that insufficient lubrication is normally present whereby overheating of the wire occurs which deteriorates the surface finish and the ductility thereof.
The prior art dry drawing processes, the improvement of which is the subject of the present invention, utilizes a solid lubricant, such as for example, solid powder soap, however due to the nature of production, there has not been proposed any method of forcedly cooling wire immediately subsequent to the emergence of the same from the die. Dry drawing of a steel wire is superior in lubrication, as well as in operational environment and drawing efficiency to the wet drawing thereof, however the processes are entirely different when comparing the same in order to devise solutions to particular problems characteristic of one or the other processes.